Thermal Migrations 



151 



breeding season. However, many species of birds inhabiting high 

 latitudes during the summer would succumb from temperature alone 

 if they remained in the far north through the winter. Other species 

 could perhaps withstand the winter cold but would succumb through 

 an indirect action of the heat factor resulting from the disappearance 

 of their food supply or from the inability of the birds to obtain the 

 larger amount of food necessary to maintain their internal tempera- 

 ture in winter. For these reasons it seems probable that the avoid- 



Modified from Neville and Perlmutter, 1941 



Fig. 5.9. Thermal migration of the winter flounder as revealed by the recapture, 

 at the points indicated, of fish tagged and released in Great South Bay, Long 



Island. 



